I love to brine a turkey for the holidays. This years Christmas turkey I think was one of the best. I have to admit that it is a store bought one, but it does wonders if you are butchering you own. (we did for Thanksgiving)
In a large pot mix 1gal of water with 2c of salt
Add 1c brown sugar, a palmful of black pepper, 5 sprigs fresh rosemary(or a couple T of dried), and a handful of fresh thyme. Simmer and stir just to dissolve salt and sugar. Add 1gal of cold apple juice. Let this cool completely.
Place your turkey into a pot large enough to hold it and the brine. (a bag lined bucket works just fine) Pour the brine over top. You have to have enough brine to cover the bird. A ziplock bag filled with ice and laid on top will keep the brine cold. If you have fridge space for it, even better. The ice will need replaced as it melts but the bag makes this easy and will keep the melting ice from diluting your brine.
I like to give mine 3 days, but anything over 24hrs will make a difference. The night before I plan to cook it I mix 2c butter with 2T thyme and 1T rosemary. You can roll this up like cookie dough and put it in the freezer overnight. When ready to cook, set out butter mix, rinse turkey well and pat dry. (Place in pan) Slice your butter mix into coins. If you wiggle your fingers around carefully you can get between the skin and the meat of the breast and thigh and place the coins in the spaces. ( find this easier than trying to smush soft butter in) I stuff my turkey with 1 apple and 1 onion quartered.
Smear the outside of the bird with plain butter. I like to melt any of the butter mix that's left and inject it into the leg, thigh and breast. Place into an oven preheated to 425' for about 40 min. or until the skin starts to turn golden. Turn the oven down to 325', and tent with foil. Ours was 12lbs and cooked about 5 hours. Baste every half hour or so.
About half an hour before it's done take the foil off and let the skin finish browning. Check temp with a meat thermometer. I quit at 160'. Set the turkey out to rest for at least half an hour. The meat just fell off the legs and thighs and the breast was amazingly juicy.